1. Field of the Invention
The present invention relates to a vehicle control system which performs an automatic stop of a drive power source during a standstill of the vehicle and includes a mechanical brake driven by an actuator.
2. Description of the Related Art
Some vehicles such as automobiles are well known which are adapted to automatically stop (idle stop) the engine of the vehicle when the vehicle is stopped in order to improve fuel economy and reduce exhaust gas. One of the vehicles with such an idle-stop function is known to automatically activate an electric parking brake serving as a mechanical brake driven by an electric actuator during an idle stop in order to prevent unintentional movement of the vehicle due to an inclination of the road surface or the like when the engine is automatically stopped (e.g., see Japanese Patent Application Laid-Open Publication No. 2004-249992).
Also known is such a vehicle which employs a plurality of sensors to detect the presence of a brake manipulation by the driver in order to ensure that unintentional movement of the vehicle is prevented with the braking force of the foot brake during an idle stop (e.g., see Japanese Patent Laid-Open Publication No. 2001-12269). Such a vehicle with the idle-stop function is also known which includes a controller for controlling the fluid pressure for the foot brake and a sensor for detecting an abnormal fluid pressure condition (e.g., see Japanese Patent Application Laid-Open Publication No. 2001-39278).
Note that use of an electric parking brake for a braking operation during an idle stop of a vehicle typically causes a less reduction in braking force resulting from a reduction in fluid pressure as compared to the use of the foot brake. This eliminates the need for providing electric power all the time to maintain the braking force, thereby providing reductions in energy consumption and improvements in reliability.
However, when an idle stop is performed while the automatic mode is released in which the electric parking brake is automatically activated during a standstill of the vehicle, the vehicle may unintentionally start to move due to loss in creep force caused by the stop of the engine or due to reduction in braking force of the foot brake caused by the stop of the brake booster. On the other hand, if an idle stop is performed not only when the automatic mode is released but also when the electric parking brake is out of order for some reason, the electric parking brake being not activated may likely cause the vehicle to start to unintentionally move.